Voltage-controlled photorefractive effect in paraelectric KTa_1−xNb_xO_3:Cu, V

Agranat, Aharon J.; Leyva, Víctor; Yariv, Amnon

doi:10.1364/ol.14.001017

Cited by 84 publications

(29 citation statements)

References 13 publications

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“…The field allows for full and rapid amplitude modulation of the diffraction efficiency of the previously recorded holograms. 6 A KLTN crystal doped with Cu, V, and Ti was grown by the top-seeded solution growth method. The crystal is grown with an excess of K in the f lux.…”

Section: 2mentioning

confidence: 99%

Fixing of photorefractive volume holograms in K_1−yLiyTa_1−xO_3

Leyva¹,

Engin

Tong

et al. 1995

Opt. Lett.

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We report the f ixing of photorefractive holographic gratings with high eff iciency in a sample of K 12y Li y Ta 12x Nb x O 3 doped with Cu, V, and Ti. Holograms are thermally f ixed through the screening of a photorefractive space-charge f ield by a nonphotoactive species at elevated temperatures. Fixed holograms are revealed by illumination at lower temperatures. Diffraction efficiencies of 25% in a 0.54-cm-thick sample are measured. Holograms undergo thermal decay with a 0.67-eV activation energy.The process by which a photorefractive holographic grating is converted to one that is not erased under illumination is referred to as fixing. The ability to fix gratings with high eff iciencies and long lifetimes is essential for holographic archival data storage applications and for the fabrication of thick holographic optical elements. Thermal fixing refers to the process by which a photorefractive space-charge grating is compensated at elevated temperatures by a mobile nonphotoactive species. At lower temperatures the thermally fixed sample is illuminated, partially erasing the initial photorefractive grating and revealing a fixed grating unaffected by illumination. Thermal fixing has been observed in ilmenite materials ͑LiNbO 3 , LiTaO 3 , Ba 2 NaNb 5 O 15 ͒ and in the perovskite material KNbO 3 . 1,2High fixed efficiencies of 98% have been achieved in a 1-cm-thick LiNbO 3 sample. The addition of Li to KTa 12x Nb x O 3 (KTN) has been found to improve the optical quality of crystals with phase transitions near room temperature. The ferroelectric phase transition occurs at a temperature that increases with both Li and Nb concentrations. Large quadratic electro-optic effects occur in the cubic paraelectric region above the phase transition, which results in high-diffraction-efficiency holograms. In this region of operation, an external electric field is required for the generation of a firstorder grating that can diffract the writing beams. The field allows for full and rapid amplitude modulation of the diffraction efficiency of the previously recorded holograms. 6A KLTN crystal doped with Cu, V, and Ti was grown by the top-seeded solution growth method. The crystal is grown with an excess of K in the f lux. The ratio of Li to K in the f lux is 0.027, and the ratio of Ta to Nb in the f lux is 0.43. A sample measuring 5.4 mm 3 5.7 mm 3 8.0 mm was cut and polished along the crystallographic axes. The OH 2 vibrational absorption band at 3512 cm 21 was measured with a Fourier-transform infrared spectrometer to have a peak magnitude of 0.41 cm 21 and an integrated intensity of 57.6 cm 22 . With the calibration results of Scherban et al., 7 this corresponds to a proton concentration of 5.76 3 10 25 mole fraction or 9.2 3 10 17 cm 23 . Metal electrodes were evaporated on the 5.4 mm 3 5.7 mm faces. The sample was placed on a thermoelectric temperature-controlled mount enclosed in a vacuum chamber. The temperature dependence of the dielectric constant was determined from measurements of the low-frequency capacitance of t...

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Section: 2mentioning

confidence: 99%

Fixing of photorefractive volume holograms in K_1−yLiyTa_1−xO_3

Leyva¹,

Engin

Tong

et al. 1995

Opt. Lett.

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“…An alternative possibility is the use of the recently developed quadratic materials that belong to the potassium tantalate niobate group. 20 These materials possess a surprisingly large PR nonlinearity with an externally applied electric field, which does not vanish even in the absence of this field, owing to a strain-induced Jahn-Teller effect.…”

Section: Design Considerationsmentioning

confidence: 99%

Self-trapping of optical beams in photorefractive media

et al. 1993

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We study the possibility of self-trapping of an optical beam in a photorefractive medium under the combined influence of diffraction and self-scattering (two-wave mixing) of its spatial frequency components. We investigate the spectrum of solutions for the resulting photorefractive spatial solitons and discuss their unique properties. Design considerations and material requirements for experimental realization of these solitons, together with specific examples, are given.

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“…For example, samples of strontium barium niobate 5 can have values of´r Х 2 3 10 4 8 3 10 4 for T Х 125 140 ± C, and we expect to be able to observe significant diffusion-driven nonlinear diffraction compensation (the effective Dn ranges in this case from 1.8 3 10 25 to 2.7 3 10 24 ). Other crystals with high´r are paraelectric potassium lithium tantalate (KTN) 6 and paraelectric potassium lithium tantalate niobate (KLTN). 7 Returning to Eq.…”

mentioning

confidence: 99%